PY-15046: Invert 'if' statement implementation

[outring]

Invert 'if' statement implementation

Inversion of if statements and conditionals is implemented. YouTrack issue PY-15046

What's supported

• Recursive conditions inversion
  • Simple comparisons and coerced expressions
  • not in and is not expressions
  • Assignment expressions
  • Multiline expressions (as good as I could)
  • and and or expressions with precence support
• If statements
  • if-only statements
  • if-else statements
  • Module, function and loops scopes with corresponding termination statements (return, raise, continue, break)
  • Comments switching
    • Inline comments after if ...: and else:
    • Multiple preceding line comments before if, else and if followup code.
    • Service comments are respected (type, pylint, noinspection)
• Conditional statements

Issues

• Had to mark switched statements for reformat in order to normalize indentation, would love to learn how to indent moved nodes explicitly without full reformat
• Preceding comments switch might be too smart and could be simplified if the behavior is confusing
• Detection of broken statements is not implemented because I couldn't find a good suitable existing examples in existing Py code, tests are there and need to be fixed
• When missing else branch is being generated, pass is being focused but probably it's too much or must be implemented with editable placeholder functionality
• Terminated statement detection using ControlFlow looks odd, not sure if it used the optimal way

[akniazev]

Regarding your questions:
I see no problem with preceding comment switch, marking to reformat and control flow usage.
Selecting pass when else branch is generated is a good idea, just move the caret there as well, otherwise it's confusing.
To detect broken conditions you can use PsiTreeUtil.hasErrorElements(ifStatement.ifPart.condition), it will return true if there are parse errors in the condition.
We've also discussed with you that something has to be done for conditions like 1 < x < 3.

Don't hesitate to contact me with any questions and thank you for the great work you're doing. 🙂